The rate at which America's kids are diagnosed with diabetes is climbing and researchers don't know why.

A first-ever study of new diabetes diagnoses of U.S. youth under age 20 found both Types 1 and 2 diabetes surged from 2002-2012.

The diagnosis of new cases of Type 2 diabetes, associated with obesity, increased about 5% each year from 2002 to 2012, the study said, while new cases of Type 1, the most common form for young people, went up about 2% every year.

The National Institutes of Health, which funded the study along with the Centers for Disease Control and Prevention, said the cause of the rise is "unclear."

"These findings lead to many more questions," explained Dr. Barbara Linder, senior advisor for childhood diabetes research at NIH's National Institute of Diabetes and Digestive and Kidney Diseases. "The differences among racial and ethnic groups and between genders raise many questions. We need to understand why the increase in rates of diabetes development varies so greatly and is so concentrated in specific racial and ethnic groups."

The study, published Friday in the New England Journal of Medicine, showed higher rates of diabetes diagnoses among minorities. Type 2 diabetes, which the CDC stated makes up about 90% to 95% of diagnosed diabetes cases, rose by 8.5% in Asian Americans ages 10-19. Blacks in the same age group saw a 6.3% increase, followed by a 3.1% bump in Hispanics and whites at fewer than a 1% increase.

Hispanics saw the biggest rate increase of Type 1 diabetes with a 4.2% increase, followed by blacks at 2.2% and whites at 1.2%

In terms of gender, girls and women 10-19 saw a 6.2% increase in Type 2 diabetes, while men and boys of the same age experienced a 3.7% increase. Across all age groups, Type 1 diabetes increased 2.2% in males and 1.4% in females.

CDC epidemiologist Dr. Giuseppina Imperatore said those who develop diabetes at a young age are at risk of developing complications from the disease earlier, lowering their quality of life, shortening life expectancy and increasing health care costs.